JPH08128875A - Flow rate measuring instrument - Google Patents

Abstract

PURPOSE: To improve the flow rate measuring accuracy of an ultrasonic flowmeter. CONSTITUTION: A flow rate measuring instrument is provided with a first vibrator 5 attached to a fluid pipe 4, second vibrator 6 which receives ultrasonic signals transmitted from the vibrator 6, repeating means 11 which repeats the transmission of ultrasonic signals between the vibrators 6 and 7 a plurality of number of times, and switching means 15 which switches the transmission and reception of the ultrasonic signals between the vibrators 6 and 7 to each other. The instrument is also provided with a flow rate calculating means 16 which calculates the flow rate of a fluid based on the difference between transmission repeating times by providing delaying time between each repetition. Thus, noise such as reflected wave can be reduced to increase a flow rate measuring accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring device for measuring the flow rate of gas or the like using ultrasonic waves.

[0002]

2. Description of the Related Art A conventional flow rate measuring device of this type is shown in FIG.
As shown in FIG.
Is provided opposite to the flow direction, ultrasonic waves are generated from the vibrator 1 in the flow direction, and when the ultrasonic waves are detected by the vibrator 2, the ultrasonic waves are again generated from the vibrator 1, and this is repeated for the time. In contrast, the ultrasonic wave was generated from the vibrator 2 against the flow, the same repetition time was measured, and the velocity of the fluid was calculated from the difference in the times.

[0003]

However, in the above conventional flow rate measuring device, noise is generated in the detection signal due to the reflection of ultrasonic waves between the transducers. That is, first, the ultrasonic signal transmitted from the oscillator 2 reaches the oscillator 3, and when this signal is amplified and compared and detected, the next trigger signal is immediately excited and the second transmission is performed. On the other hand, oscillator 3
The ultrasonic signal reflected by is directed to the transducer 2, and when the second signal reaches the transducer 3 and the trigger of the third signal starts, the first reflected signal reaches. This is because the propagation time of ultrasonic waves is about 500 microseconds, whereas the time for signal amplification and comparison and retrigger is 0.1 microseconds or less, which is extremely short. Therefore, since the reflected wave is received at the time of transmission, it becomes a transmission signal having a disturbed waveform. Further, the reflected signal of the first time is reflected by the vibrator 2 again, goes to the vibrator 3, is superimposed on the transmitted signal of the third time, and reaches the vibrator. The detection signal is affected by these reflected signals and is measured. Since the arrival time of this reflected wave varies depending on the flow velocity in the conduit 1, it receives complicated noise and affects the measurement accuracy, making it difficult to perform high-precision measurement.

The present invention is intended to solve the above problems, and its main purpose is to improve the accuracy of flow rate measurement.

[0005]

In order to achieve the above object, the flow rate measuring device of the present invention has the following configuration.

That is, the first oscillator and the second oscillator provided in the fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the ultrasonic oscillator, and mutual ultrasonic transmission between the oscillators. It is provided with repeating means for performing a plurality of times, delay means for delaying signal transmission at the time of repeating, and flow rate calculating means for calculating the flow rate based on the cumulative time of ultrasonic wave propagation.

Further, the first oscillator and the second oscillator provided in the fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and mutual ultrasonic transmission between the oscillators. Repeating means for performing a plurality of times, delay means for delaying signal transmission at the time of repeating, time setting means for setting a delay time of the delay means, setting changing means for arbitrarily changing the time setting means, and ultrasonic wave transmission. And a flow rate calculating means for calculating the flow rate based on the cumulative time.

Further, a first oscillator and a second oscillator provided in the fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and mutual ultrasonic transmission between the oscillators. Repeating means for performing a plurality of times, delay means for delaying signal transmission at the time of repeating, time setting means for changing the delay time at the end of repetition, and flow rate calculating means for calculating the flow rate based on the cumulative time of ultrasonic wave propagation. Be prepared.

In addition, a first oscillator and a second oscillator provided in the fluid conduit for transmitting and receiving an ultrasonic signal, switching means for transmitting and receiving the oscillator, and mutual ultrasonic transmission between the oscillators. Repeating means for performing a plurality of times, delay means for delaying signal transmission at the time of repeating, time setting means for setting a delay time of the delay means, and the time setting means so that the sum of delay times during repetition becomes a constant value. And a flow rate calculation means for calculating the flow rate based on the cumulative time of ultrasonic wave propagation during repetition.

Further, the first oscillator and the second oscillator provided in the fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and mutual ultrasonic transmission between the oscillators. Repeating means for performing a plurality of times, delay means for delaying signal transmission at the time of repeating, time setting means for setting a delay time of the delay means, repeating transmission from upstream to downstream and from downstream to upstream. Equal setting means for arbitrarily changing the time setting means so that the total sum of respective delay times during repeated transmission becomes equal, and flow rate calculation means for calculating the flow rate based on the cumulative time of ultrasonic wave transmission during repetition. It is equipped with.

The first and second oscillators provided in the fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillators, and mutual ultrasonic transmission between the oscillators. Repeating means for performing a plurality of times, delaying means for delaying signal transmission at the time of repeating, external setting means for changing the setting means from the outside, and flow rate calculating means for calculating the flow rate based on the cumulative time of ultrasonic wave propagation. It is equipped with.

Further, the first oscillator and the second oscillator provided in the fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the ultrasonic oscillator, and mutual ultrasonic transmission between the oscillators. Repeating means for performing a plurality of times, delaying means for delaying signal transmission at the time of repeating, flow rate calculating means for calculating a flow rate based on accumulated time of ultrasonic wave propagation, and delay time of the delaying means according to the value of the flow rate calculating means. And a time setting means for setting.

[0013]

The present invention has the above-mentioned structure and delays repeated ultrasonic wave oscillation to reduce the influence of reflected waves.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a first vibrator 5 that transmits ultrasonic waves and a second vibrator 6 that receives ultrasonic waves are arranged in the flow direction in the middle of the fluid conduit 4. Reference numeral 7 is a transmitting circuit to the first vibrator 5, 8 is an amplifier circuit for a signal received by the second vibrator 6, and the amplified signal is compared with a reference signal by a comparison circuit 9,
When a signal higher than the reference signal is detected, the frequency setting circuit 10
The delay circuit 12 is repeated by the repeater 11 for the number of times set in
After delaying the signal with, the trigger circuit 13 repeatedly transmits the ultrasonic signal. The time when the number of times set by the number-of-times setting circuit 10 is repeated is obtained by the time measuring means 14 such as a timer counter. Next, the switching means 15
Switching the transmission and reception of the oscillator 5 and the second oscillator 6, the second oscillator
An ultrasonic wave signal is transmitted from the vibrator 6 to the first vibrator 5, that is, from the downstream side to the upstream side, and this transmission is repeated as described above to measure the time. Then, from the time difference, the flow rate calculating means 16 obtains the flow rate value in consideration of the size of the pipeline and the flow state.

Next, the transmission / reception signal of the vibrator will be described. FIG. 2 shows a case where the ultrasonic wave signal transmitted from the first vibrator 4 is received by the second vibrator 5. The first oscillator signal burst-transmitted from the first oscillator 4 is received by the second oscillator 5 as the first reception signal, amplified and compared, and is triggered again via the delay circuit 11 to become the second oscillator signal.
On the other hand, a part of the ultrasonic wave of the second oscillator is reflected and travels toward the first oscillator and arrives at the first oscillator, and the second oscillation signal is received and is again transmitted through the delay circuit 11 as the third oscillation signal. There is a difference from the transmission time by about twice the delay time Td of the delay circuit. Further, the first oscillator signal is reflected by the first oscillator 5 and heads for the second oscillator 6, but a time difference of twice the delay time Td is generated from the third received signal which the third oscillator signal reaches. FIG. 3 shows the relationship between transmission and reception when the delay circuit 11 is not provided. The third transmission signal corresponds to the reflected wave of the first transmission signal, and the third reception signal includes the third transmission signal and the first transmission signal. It will overlap with the reflected wave twice. Thereafter, all of the transmissions and receptions repeated the number of times set by the repetition number setting circuit 10 are affected by the reflected wave, and an accurate transmission or reception signal cannot be obtained. If the received signal does not re-trigger unless it exceeds the reference signal, the delay time Td of the delay circuit 11 is at least 1.5 times the time width Tr of the received signal obtained by the burst transmission of ultrasonic waves, so that the influence of the reflected wave will occur. I do not receive it. Although this delay time lengthens the time required for measurement, the ultrasonic wave propagation time is 500 microseconds per time, whereas the delay time is about 20 microseconds, which is not a large delay.

FIG. 4 shows a second embodiment, in which the time of the delay circuit can be arbitrarily changed by the time setting circuit 17, for example, the setting variable circuit can be made proportional to the length of the burst signal or a certain time. As described above, the influence of the periodic noise can be reduced by changing it at random.

FIG. 5 shows a third embodiment, which is a timing circuit 14
Signal is used to change the delay time setting of the time setting circuit 17, and the delay time is changed after the repetition is completed and the time is measured, that is, the flow rate is calculated. It is something to measure.

FIG. 6 shows a fourth embodiment, in which the delay time is changed so that the total sum during the repetition of the delay time becomes constant in the total sum setting circuit 19. Delay time is added.

FIG. 7 shows a fifth embodiment. Although the total sum of the delay times can be changed, the delay time is equally set during the repetition from upstream to the downstream and the repetition from downstream to upstream. To keep them equal.

FIG. 8 shows a sixth embodiment, in which the delay time can be arbitrarily changed by an external setting circuit 21 such as a variable resistor and is adjusted at the time of production of installation work.

FIG. 9 shows a seventh embodiment, in which the delay time is changed according to the value of the flow rate calculating means 16, and when the flow rate is large, it is reflected from the second oscillator 6 and the first oscillator. The arrival time of the ultrasonic wave traveling toward 5 is delayed because it travels against the flow, and the delay time may be insufficient. Therefore, the delay time is corrected according to the flow amount. That is, the value of the delay time is increased when the value of the flow rate is large, the value of the delay time is decreased when the value of the flow rate is small, and the relative delay time is kept constant.

[0022]

As is apparent from the above description, the following effects can be obtained by the flow rate measuring device of the present invention. (1) A first oscillator and a second oscillator provided in a fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and ultrasonic transmission between the oscillators a plurality of times. Since the repeating means for performing, the delay means for delaying the signal transmission at the time of the repetition, and the flow rate calculating means for calculating the flow rate based on the accumulated time of the ultrasonic wave propagation are provided, the noise due to the reflected signal of the ultrasonic transducer is reduced. The measurement accuracy can be improved. (2) A first oscillator and a second oscillator provided in a fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and ultrasonic transmission between the oscillators a plurality of times. Repeating means for performing, delay means for delaying signal transmission at the time of repeating, time setting means for setting a delay time of the delay means, setting changing means for arbitrarily changing the time setting means, and accumulation of ultrasonic wave propagation. Since the flow rate calculation means for calculating the flow rate based on time is provided, noise can be prevented by changing the delay time even if the length of the received signal changes, and it is possible to cope with reflected signals other than the vibrator. Yes, the circuit can be standardized. (3) A first oscillator and a second oscillator provided in the fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and ultrasonic transmission between the oscillators a plurality of times. It comprises a repeating means for performing, a delay means for delaying the signal transmission at the time of repeating, a time setting means for changing the delay time at the end of the repetition, and a flow rate calculating means for calculating the flow rate based on the cumulative time of ultrasonic wave propagation. Therefore, since the delay time is not changed during the repetition, the flow rate calculation based on the time measurement is easy and the error is small. (4) A first oscillator and a second oscillator provided in a fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and ultrasonic transmission between the oscillators a plurality of times. Repetition means for performing, delay means for delaying signal transmission during the repetition, time setting means for setting the delay time of the delay means, and the time setting means so that the total sum of the delay times during the repetition becomes a constant value. Since the total sum setting means to change to and the flow rate calculation means to calculate the flow rate based on the accumulated time of the ultrasonic wave propagation during the repetition are provided, the delay time can be changed during the repetition and the time of the reflected wave can be changed. Since it is possible to deal with such fluctuations and the total sum of delay times is constant, the flow rate calculation based on the timing means is easy and the error is small. (5) A first oscillator and a second oscillator provided in the fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and ultrasonic transmission between the oscillators a plurality of times. Repeating means for performing, delay means for delaying signal transmission at the time of repeating, time setting means for setting a delay time of the delay means, repeating transmission from upstream to downstream and repeating transmission from downstream to upstream And a flow rate calculation means for calculating a flow rate based on the cumulative time of ultrasonic wave propagation during repetition. Therefore, the delay time can be changed during repetition, and it is possible to respond to the temporal fluctuation of the reflected wave, and the total sum of the delay times from upstream to downstream and from downstream to upstream is constant. Since the offset when computing the flow rate determines the difference error is less easily flow calculation. (6) A first oscillator and a second oscillator provided in the fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and ultrasonic transmission between the oscillators a plurality of times. A repeating means for performing the delay, a delay means for delaying signal transmission during the repeating, an external setting means capable of changing the setting means from the outside, and a flow rate calculating means for calculating a flow rate based on an accumulated time of ultrasonic wave propagation. Therefore, the setting of the delay time can be changed at the time of production or installation, and the measurement accuracy is high. (7) A first oscillator and a second oscillator provided in the fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and ultrasonic transmission between the oscillators a plurality of times. Repeating means for performing, delaying means for delaying signal transmission at the time of repeating, flow rate calculating means for calculating flow rate based on accumulated time of ultrasonic wave propagation, and setting delay time of the delaying means by the value of the flow rate calculating means Since the reflected wave is delayed by a fixed time regardless of the value of the flow rate, the flow rate accuracy is high.

[Brief description of drawings]

FIG. 1 is a control block diagram of a flow rate measuring device according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram of a transmission / reception signal of the device.

FIG. 3 is a waveform diagram of a transmission / reception signal of a conventional flow rate measuring device.

FIG. 4 is a control block diagram of a flow rate measuring device according to a second embodiment of the present invention.

FIG. 5 is a control block diagram of a flow rate measuring device according to a third embodiment of the present invention.

FIG. 6 is a control block diagram of a flow rate measuring device according to a fourth embodiment of the present invention.

FIG. 7 is a control block diagram of a flow rate measuring device according to a fifth embodiment of the present invention.

FIG. 8 is a control block diagram of a flow rate measuring device according to a sixth embodiment of the present invention.

FIG. 9 is a control block diagram of a flow rate measuring device according to a seventh embodiment of the present invention.

FIG. 10 is a control block diagram of a conventional flow rate measuring device.

[Explanation of symbols]

 4 Fluid Pipe 5 First Oscillator 6 Second Oscillator 11 Repeating Means 12 Delaying Means 14 Delaying Means 14 Timing Means 15 Switching Means 16 Flow Rate Calculating Means 17 Time Setting Means 18 Setting Changing Means 19 Total Setting Means 20 Equal Setting Means 21 External Setting Means

Claims (9)

[Claims] 1. A first oscillator and a second oscillator provided in a fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and mutual ultrasonic transmission between the oscillators. A flow rate measuring device comprising: a repeating unit that performs a plurality of times; a delay unit that delays signal transmission during the repetition; and a flow rate calculating unit that calculates a flow rate based on the cumulative time of ultrasonic wave propagation. 2. The flow rate measuring device according to claim 1, wherein the setting time of the delay means is 1.5 times or more the ultrasonic reception signal time. 3. A first oscillator and a second oscillator provided in a fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the ultrasonic oscillator, and mutual ultrasonic transmission between the oscillators. Repeating means for performing a plurality of times, delay means for delaying signal transmission at the time of repeating, time setting means for setting a delay time of the delay means, setting changing means for arbitrarily changing the time setting means, and ultrasonic wave transmission. And a flow rate calculation means for calculating the flow rate based on the accumulated time of the flow rate measurement device. 4. The flow rate measuring device according to claim 3, wherein the setting variable means changes randomly. 5. A first oscillator and a second oscillator provided in a fluid conduit for transmitting and receiving an ultrasonic signal, switching means for transmitting and receiving the oscillator, and mutual ultrasonic transmission between the oscillators. Repeating means for performing a plurality of times, delay means for delaying signal transmission at the time of repeating, time setting means for changing the delay time at the end of repetition, and flow rate calculating means for calculating the flow rate based on the cumulative time of ultrasonic wave propagation. A flow rate measuring device equipped. 6. A first oscillator and a second oscillator provided in a fluid conduit for transmitting and receiving an ultrasonic signal, switching means for transmitting and receiving the oscillator, and mutual ultrasonic transmission between the oscillators. Repeating means for performing a plurality of times, delay means for delaying signal transmission at the time of repeating, time setting means for setting a delay time of the delay means, and the time setting means so that the sum of delay times during repetition becomes a constant value. A flow rate measuring device comprising a total sum setting means for arbitrarily changing the flow rate and a flow rate calculation means for calculating the flow rate based on the cumulative time of ultrasonic wave propagation during repetition. 7. A first oscillator and a second oscillator provided in a fluid conduit for transmitting and receiving an ultrasonic signal, switching means for transmitting and receiving the oscillator, and mutual ultrasonic transmission between the oscillators. Repeating means for performing a plurality of times, delay means for delaying signal transmission at the time of repeating, time setting means for setting a delay time of the delay means, repeating transmission from upstream to downstream and from downstream to upstream. Equal setting means for arbitrarily changing the time setting means so that the total sum of respective delay times during repeated transmission becomes equal, and flow rate calculation means for calculating the flow rate based on the cumulative time of ultrasonic wave transmission during repetition. Flow rate measuring device equipped with. 8. A first oscillator and a second oscillator provided in a fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the oscillator, and mutual ultrasonic transmission between the oscillators. Repeating means for performing a plurality of times, delay means for delaying signal transmission at the time of repeating, time setting means for setting a delay time of the delay means, external setting means for changing the time setting means from the outside, ultrasonic transmission A flow rate measuring device comprising a flow rate calculating means for calculating a flow rate based on the cumulative time of the rice field. 9. A first vibrator and a second vibrator provided in a fluid conduit for transmitting and receiving ultrasonic signals, switching means for transmitting and receiving the vibrator, and mutual ultrasonic transmission between the vibrators. Repeating means for performing a plurality of times, delaying means for delaying signal transmission at the time of repeating, flow rate calculating means for calculating a flow rate based on accumulated time of ultrasonic wave propagation, and delay time of the delaying means according to the value of the flow rate calculating means. And a time setting means for setting the flow rate measuring device.